1. Field of the Invention
The present invention relates to a method and device for determining a disk size and stopping a rotating disk and, more particularly, to a method and device for determining the presence or absence of a disk and/or the disk size and calculating an exact brake-voltage applying time for stopping a rotating disk without the use of frequency generator (FG) signals.
2. Description of the Background Art
FIG. 1 shows a block diagram of a general disk device. As shown, the disk device of FIG. 1 includes an optical pickup 11 detecting signals recorded on an optical disk 10; a disk tray 19 receiving the optical disk 10 therein; a radio frequency (RF) unit 12 producing a binarized signal and servo error signals by selectively combining the detected RF signals; a digital signal processor (DSP) 13 restoring original data from the binarized signal; a spindle motor 14 rotating the disk 10 at a high speed; a sled motor 15 moving the pickup 11 radially on the disk 10; a driving unit 16 driving the spindle motor 14 and the sled motor 15; and a controller 17 controlling the overall operation of the disk device.
The spindle motor 14 includes a frequency generator (FG) sensor 141 that produces a pulse train (called an ‘FG signal’ in general) during the rotation of the motor 14. The FG signal is applied to the controller 17 as shown in FIG. 1.
The disk device configured as above uses the FG signal from the FG sensor 141 to judge whether or not a disk has been placed on a disk tray and whether the placed disk is a 8 cm disk (i.e., in diameter), or a 12 cm disk. The details of this judging operation are as follows.
When the disk tray 19 having the disk 10 thereon is closed, the controller 17 applies a driving voltage to the spindle motor 14 for a predetermined time Tc through the driving unit 16.
It is well recognized that the lighter the disk is, the faster it rotates by an applied constant force. In other words, the lighter a load applied to the spindle motor 14 is, more pulses the FG sensor 141 outputs for a given time window. Therefore, the controller 17 counts a number of pulses in the FG signal input for the duration of the time Tc and compares this counted value (pulse number) with two references TNL and TNH, where TNL<TNH. If the counted value is greater than TNH, the controller 17 judges that there is no disk. If the counted value is between TNH and TNL, it judges that the placed disk is a 8 cm disk. If the counted value is smaller than TNL, then it judges the placed disk is a 12 cm disk.
Because the number of pulses per a unit time, e.g., one second, is indicative of a disk rotation speed, the disk device of FIG. 1 uses the FG signal output from the FG sensor 141 to determine the duration and/or amplitude of a brake voltage suitable to stop a rotating disk.
For example, if a disk stop is requested during the rotation of the disk, the controller 17 counts pulses of the FG signal for a predetermined time period to know how fast the spindle motor 14 is rotating, and applies a brake voltage during a time suitable to stop that speed. As a result, the rotating spindle motor 14 slows down and ultimately stops.
If the brake voltage applying time were not determined properly by using the above-discussed method, the rotating disk would not be stopped properly or would be rotated in a reverse direction. If the user opens the disk tray while the disk is still rotating thereon, the opening of the disk tray will cause damage to the rotating disk or injury to the user.
Another method to stop a rotating disk is to apply a brake voltage until no pulse is output from the FG sensor 141. This method may ensure that the rotating disk is appropriately stopped.
As aforementioned, the FG sensor in the spindle motor of a general disk device is used to determine the presence or absence of a disk in the disk device, and/or to stop the disk rotating in the disk device. However, equipping the disk device with an FG sensor increases the size and production cost of the disk device. Since disk devices are generally mass produced, there is a need to reduce the size and production cost of the disk device, if possible, by eliminating one or more parts of the general disk device.